Good Morning,

I have a couple of questions on venting my plumbing. I recently purchased a major fixer home and the home is up on pylons. The homes sewer system is on a Leach system with one tank. My question is after I finished remodeling the interior I noticed that there is no main stack vent coming up from the 4" sewer drain leading out to the roof. So there is no venting for the sinks or shower. Oh yes I have had lots of issues with draining everything in the home but now the home is live able so I have to do something. The septic tank sewer drain to the house is four inches in diameter. The sewer drain pipe runs about 12' under ground and then takes a 90 degree turn vertically up to the toilet. I have about two feet of exposed pipe coming up out of the ground that connects to the toilet. Somebody prior actually had the plumbing draining into that main but has been cut and capped.

1st Question, Can I run a vent pipe off of that exposed two feet of 4" drain pipe that leads out of the ground from the septic pipe to the toilet.

2nd Qusetion, if i can vent off that 4" pipe can it run horizontal at an 1/8" per foot slant at about 10' in total length then go vertical at about 8' in height then go out of the roof. My utility room has an exposed interior wall that i can run the pipe up the wall out to the roof.

3rd Question, what size main stack vent pipe if all the above is possible? I was thinking 3" main stack vent coming off the 4" and then 1.5 vents for two sinks,one shower and one toilet that would connect to that main stack horizontal portion of the pipe.



I apologize if it's hard to picture and understand what im asking, but any help would be greatly appreciated. I would call a plumber but my finances are pretty limited right now. Thank you for any help you maybe able to give.

you can run a 3" pipe thru the roof as you described.

Thank you for your help.



Edited 1 times.

that may not be the only vent you need. it all depends on how everything was plumbed

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I was going with the main vent as described and then put in air admittance valves to the two sinks. I was really conserned about the main vent being horizontal. I was also thinking of adding 1.5 size pipe for vents off the shower and tie it into the 3" main vent pipe. My biggest concerns have been the vents in general having to run horizontal for about 10' before the vent pipes can run vertical at about 8'high. I guess this will be better nothing. Thank you.